Core-shell particles having a crosslinked elastomeric core and a thermoplastic shell are known. Such particles are particularly useful when blended with thermoplastics to decrease their brittleness. One class of known core-shell particles includes a crosslinked polyorganosiloxane (silicone) core and a vinyl polymer shell. These silicone impact modifier (SIM) particles have been evaluated as impact modifiers for various thermoplastics, but their utility is limited by apparently poor bonding between the particles' cores and shells. There is therefore a need for new methods of preparing SIM particles that provide improved bonding between core and shell.